System for controlling film motion

ABSTRACT

Photographic film is reeled and a loop thereof is included between the payout reel and the takeup reel. A capstan engages the film in the loop and controls movement of the film past a beam recorder in accordance with the sprocket holes in the film. The capstan is controlled to cause the beam to record equispaced lines and sequential video frames are particularly positioned relative to the sprocket holes in the film. In one embodiment of the invention the loop is isolated by a sprocket wheel and a sprocket capstan engages the film in the loop. The speed of the sprocket wheel is controlled so that loop branches between it and the capstan have constant length to thereby indirectly couple the wheel and the capstan. A high inertia idler near the recording area suppresses high frequency vibrations in the film. In a second embodiment of the invention the smooth capstan is used in place of the sprocket and capstan. In a third embodiment of the invention, a pair of compliance arms are used to control servoing of the payout and takeup reels and a smooth capstan engages the film in the loop.

United States Patent [1 1 Bradford et at. I

SYSTEM FOR CONTROLLING FILM July 23, 1974 [541 2912,48? 11/1959 Horsleyl78/6.'i A MOTION a 1 Primary Examiner-Howard W. Britton [75] gn h gg ggt zgggs Attorney, Agent, or Firm-Smyth, Roston & Pavitt Ventura;Richard F. Dubhe;

Richard D. Ebbinga, both of [57] ABSTRACT Camarillo, all of Calif.Photographic film is reeled and a loop thereof is included between thepayout reel and the takeup reel. A [73] Asslgnee' Mmnesota Mmmg &Manufacturmg capstan engages the film in the loop and controls CompanyPaul movement of the film past a beam recorder in accor- 22 il M 1972dance with the sprocket holes in the film. The capstan is controlled tocause the beam to record equispaced [21] Appl- 251,219 lines andsequential video frames are particularly posi- Rd t d Us, A li ti D ttioned relative to the sprocket holes in the film. In one [63]Continuation of Ser- 19 614 March 16 0 embodiment of the invention theloop is isolated by a abandoned, which is a continuation-impart of Ser.Sprocket wheel and a Sprocket capstan engages No. 829,666, June 2, 1969,abandoned, film in the loop. The speed of the sprocket wheel [8controlled so that loop branches between it and the [52] US. Cl.....178/6.7 A, l78/6.6 P, 178/DIG. 28, capstan have constant length tothereby indirectly 226/78, 352/27 352/30 couple the wheel and thecapstan. A high inertia idler 51 Int. (3...... Gllb 7/08, G1 lb 15/54,H04n 5/86 near the recording area Suppresses high frequency 53 Field fSearch 17 3 A, 5 p, mg 23; brations in the film. In a second embodimentof the 226/78; 352/27, 30 invention the smooth capstan is used in placeof the I sprocket and capstan. In a third embodiment of the 5 R fe n itd invention, a pair of compliance arms are used to con- UNITED STATESPATENTS trol servoing of the payout and takeup reels and a 2 442 4006/1948 Collins 226/78 smooth capstan engages the film in the loop.2:807:978 10/1957 Holman 226/78 34 Claims, 7 Drawing Figures j 7 iVazwum {ax/em I J/rc/mn 61/ I I 22 J,

16' E E M I 21 I i t 1 fllha/mzm/ 42 M E Q JZ/fifiii 1 tion relates to afilm transport system cooperating with an electron beam for recordinginformationdirectly on photographic'film, in a line-for-line scanningpattern 1 It is essential for this type of recording to match thepositions of the video frames as recorded on the film to the positionsof the sprocket holes thereof, as the posi- .and arranged in sequentialframes, the lines extending transverse to extension and motion of thefilm.

tions of the sprocket holes determine the positioning of the film duringreproduction. In addition, of course, the lines must berecorded to becompletely straight and sequential lines must be equidistantly spaced.For several reasons,- it is of particular advantage to control therecording process in such a mannerthat the film runs continuously andnot intermittently. This mode of recording permits that the beam bedeflected in one direction only, transverseto the direction of filmmotion. Intermittent recording in the respective standstill position ofthe film during recording each frame has the ad vantage that theaccuracy of the control is exclusively a problem of electronics and doesnot depend on the constancy of physical motion. But the discontinuousprocess of recording has the disadvantage that the available period formoving and positioning the film during the vertical sync period israther short, so that the film may still vibrate when recording hasalready begun.

The invention, therefore, relates particularly to film recording inwhich the film is moved continuously through an area where intersectingan electron beam, which is line-for-line deflected and intensitycontrolled, in a conventional manner, as far as TV technique isconcerned, but which is not deflected in a vertical direction. It ispresumed that the video signal controlling the electron gun is amanifestation of video signals on a complete frame basis, withoutinterlacing of sequential fields.

The motion of a film at a constant speed, particularly during recording,poses variousproblems. For various reasons the film will tend to vibrateand oscillate, tending to cause the recording lines to appear jitteryand variably spaced. In two of the embodiments of the invention, thefilm is moved by means of a sprocket wheel which is, of course,conventional for film transport. The advantage of sprockets is thatslippage-free coupling relationship between sprocket wheel rotation andfilm advance is positively ensured. However, the

film, as well asthe sprocketwheel, tend to move irregularly due toexternal disturbances in the mechanical system. A particular source ofsuch disturbances is the film feeding, reeling and rewinding mechanism,and the mechanical system which includes the sprocket drive must beexpected to undergo irregular motions. Moreover, the sprockets of asprocket wheel do not consistently enter accurately a film sprocket holewithout scraping against the edges of the hole. Additionally, the motionhas to be slaved to the vertical frame rate,

which means that for each vertical sync pulse period film has to beadvanced for a particular distance, equivalent to a particular number ofsprocket holes therein.

In accordance with a first embodiment of the invention, it is suggestedto isolate a film loop of fixed length from the film feeding, reelingand takeup device. Within the loop the film is stan, and the averagespeed with which the film passes through the loop is indirectlycontrolled from the sprocket capstan. The sprocket capstan is narrowbandwidth position controlled for advancing the film in 'synchronismwith the sequential frames of the video signal to be recorded and thesprocket holes in the film.

The sprocket capstan is broadband speed controlled to obtain straightand equidistantly spaced recording lines while maintainingthe controlledposition as between the video frames as a whole and the sprocket holes.-A fine resolution tachometer disc bearing also markers representing thecapstan sprockets is coupled to the sprocket capstan and its progressiveposition'is compared with reference signals for speed controlling thesprocket capstan in a manner which also maintains or tends to maintain afixed relation between the sprocket holes and the frame sequence. 1

The system, in accordance with the first embodiment of the invention,therefore, includes equipment for servoing the position of the sprocketcapstan which directly moves the film past the recording area, whereby{the progression of sprocket holes is slaved to the se quence of thevertical sync pulses to thereby establish a fixed position relationshipbetween sequential frames and the sprocket hole pattern. A narrowbandcontrol loop using the capstan markers establishes this control.Broadband control using the high resolution disc pattern establishessmooth film advance for straight line recording without disturbing theposition control either by directly coupling the two controls or byhaving them operate alternatively, using the fixed relationship ofsprocket markers and high resolution pattern on the .tachometer disc.

In addition, however, it must be observed that the tight fit as betweenseveral of the sprockets of the capstan and thecorrespondingnumber ofsprocket holes in the film will cause the respective next sprocket toenter a sprocket hole to scrape along one or several edges of that hole,thereby setting up vibrations which are independent from the sprocketcapstan and its speed. Therefore, high frequency motion of the film inthe vicinity of the recording area is reduced or eliminated in two ways,one of which includes the broadband control.

First, the high resolution tachometer provides a sequence of relativelyhigh frequency pulses, which are compared in phase and frequency with asequence of pulses derived from the video signal. Any phase and/orfrequency difference on a broadband basis will cause the sprocketcapstan drive to change speed and relative phase position temporarily,and the resulting feedback loop operates in that the sprocket capstan isdriven so as to maintain fixed phase relation between the ta chometerpulses and the high frequency signals derived from the video signal.

In the preferred form of practicing the invention, the video frameposition control compares the vertical sync pulses and the sprocket holepositions and the comparison is used to provide the reference signal forthe advanced by a sprocket capbroadband speed control of the sprocketcapstan. The

motion of the sprocket capstan as represented by the high resolutiontachometer pulses tracks variations in the frame sequence on a lowfrequency basis as the latter when undergoing changes will cause onlylow frequency (narrow bandwidth) changes in the reference signalsoperating on the broadband loop for fine speed control.

The second speed control of the tape takes care of momentary phasedifferences between the progressing video signal and sprocket capstanrotation not compensated by the control and resulting from theprogressing engagement of sprockets with sprocket holes. A highinertiaidler is frictionally coupled to the film in the vicinity of therecording region and establishes nodes within the oscillation patternset up in the film when the sprocket scrapes edges of the sprocket hole.

The film moves accurately where gripped by the sprocket capstan and inthe immediate vicinity thereof, but the film reeling mechanismestablishes irregularities, as stated. Therefore, the film as passingthrough the recording area is isolated from the film reeling mechanismin a manner which permits film advancing past the recording area inaccordance with the accuracy of motion as provided by the sprocketcapstan. For isolation of a portion of the film, use is made of a knownexpedient which comprises another sprocket wheel engaging the film inessentially two diametrically opposite locations to form a loop, wherebyat any instant the amount of film fed into the loop equals the amountfed out of the loop. The sprocket capstan as well as the recording areaoperate the film withinthat loop.

As stated above, the sprocket wheel is indirectly coupled to the firstsprocket, and particularly to the drive thereof, through a servo system.The servo system for the isolation sprocket wheel tends to maintain theamount of film constant between sprocket capstan and, for example,between the point where the film leaves theloop. As the total amount offilm within the loop is constant at any instant by operation of thesprocket wheel itself, the control indirectly maintains also the amountof film between sprocket capstan and the loop entrance constant. Thequantity of film extending between sprocket capstan and loop exit ismonitored by a-compliance arm operating also as a feeler. The filmisolation sprocket wheel is speed controlled to maintain that arm in aparticular position, thereby to maintain a particular quantity of filmbetween loop exit and sprocket capstan and to thereby establish arotational relationship between sprocket wheel and sprocket capstan,which is equivalent to a fixed coupling without, however, thedisadvantage of any mechanical feedback effect of the sprocket wheelupon sprocket capstans as it would occur in the case the sprocket wheelswere coupled by gearing and thelike.

In a second embodiment of the invention, a smooth capstan is used in theloop to advance the film in place of the sprocket capstan of the firstembodiment. In addition to the use of a smooth capstan, the secondembodiment of the invention includesa direct monitoring of the sprocketholes of the film in the vicinity of the smooth capstan in place of theindirect monitoring of the sprocket holes by the use of the tachometerdisc of the first embodiment of the invention.

A third embodiment of the invention includes the smooth capstan in theloop and the direct monitoring of the sprocket holes in the vicinity ofthe smooth capstan and, in addition, eliminates the sprocket wheel andprovides for a pair of compliance arms for use in directly servoing thepayout and takeup reels.

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as theinvention, it is believed that the invention, the objects and featuresof the invention and further objects, features and advantages thereofwill be better understood with reference to the following descriptiontaken in connection with the accompanying drawings, in which:

FIG. 1 is a schematic view of a first embodiment of the invention;

FIG. 1a is a plan view of a detail particularly of the tachometer discemployed in the system shown in FIG.

FIGS. 2 and 3 show details of the recording area respectively insectional view in two orthogonal planes;

FIG. 4 is a modification of the system shown in FIG. 1;

FIG. 5 is a schematic view of a second embodiment of the invention; and

FIG; 6 is a schematic view of a third embodiment of the invention.

Proceeding now with the details of the description of the drawings, inFIG. 1 thereof there is illustrated a block diagram and partially aschematic construction view of the film advance and transport system, inaccordance with the first embodiment of the present in vention. There isshown a payout reel 10 for unexposed film 1, and a film takeup reel 11receiving the exposed film. The payout reel 10 is mounted for freereeling, whereas reel 11 is driven by a motor 12 for tensioning of thefilm in advancing direction. The film must, of course, be maintained ina light-tight environment. Moreover, it is a principal aspect of theenvironment in which the invention is practiced that the film betransported and maintained in a low pressure region during operation sothat a portion of the film can be brought in open contact with a nearvacuum in which an electron beam is produced. Low pressure encapsulationis denoted schematically with reference numeral 2 in FIG. I. Theelectron beam is produced inside of a casing 15' having an exit window16 for the beam. The window 16 is open to the interior of encapsulation2 but film 1 passes across that open window 16, and to some extentcloses it. Thus, a high vacuum can readily be maintained in casing 15 byoperation of a vacuum system 17. The pressure differential betweenchambers 2 and 15 operates for slight suction of the film against thewindow.

The electron gun in casing 15 is intensity controlled by operation of avideo signal source 20 of conventional design; it can be any source-onecan think of a remotely positioned TV camera-or source 20 could be amagnetic video tape which is currently being reproduced, etc.

Assuming that the video signal provided by source 20 is a composite one,then a sync separator 21 separate therefrom the horizontal and verticalsync pulses. The horizontal sync pulses control the horizontaldeflection of the electron beam in system 15. There is no verticaldeflection of the electron beam. The method employed in the system to bedescribed is designed so that the tape runs continuously and the videosignal is line-for- .line recorded by direct interaction of electrons ofthe spacing. Fo'r this, the film has to be transported at a veryaccurately constant rate of speed'with as little temporary speedvariations represented by high and medium frequency film vibrations aspossible. Moreover, the recording should be made such that there is afixed periodic position relation between the sprocket holes in the filmand the recorded frames. For the sake of convenience, reference is madeto a newer type of 16 mm. film with fairly wide spaced sprocket holesand in which'there is one sprocket hole per frame. This, however, is notessential in principle for practicing-the invention but facilitatesexplanation particularly of certain number relations.

Recording is carried out in a portion of film 1 which is mechanicallyisolated from payout reel 10, as well as from takeup reel 11. Thisisolation is provided in a manner known, per se, by means of a sprocketwheel 30 which can be regarded as an auxiliary film drive. The teeth ofthe sprocket wheel engage the sprocket holes of the film, whereby filmfrom the payout reel is gripped at region 31 by a few of the teeth ofthe sprocket wheel, passing into a loop 33 which includes the recordingarea and is gripped again by sprockets of wheel30 in region 32 to be fedtoward takeup reel 11. inherently sprocket wheel 30 feeds precisely thesame amount of film into loop 33 as it withdraws therefrom. Thus,between regions 31 and 32 there is always a definite length of film,regardless of the speed of wheel 30 equivalent of a fixed number ofsprocket holes. The re gions 31 and 32 can be defined, for example, morespecifically as two oppositely located stationary points where the filmis positively gripped by the sprocket wheel. Should there be, foranyreason, atendency to feed more film into the loop, more will bewithdrawn as the loop is not capable by itself of storing more or lessthan a fixed amount of film given by the number of sprocket holesbetween point 31, along the film up to point 32. Complete isolation ofthe loop from the film storage arrangement 10-11 would seem to requireforced constant speed of sprocket wheel 30. This, however, would noteliminate film speed irregularities within film loop 33. Therefore, theisolation is a controlled one in that sprocket wheel 30 is controlled independence upon cinditions in the loop as they may vary due tocontrolled film speed in the vicinity of window 16. For this weturnfirst to the film drive providing the required speed at window 16.

The film is pulled past the recording window 16 by operation of acapstan sprocket 40, which is driven by a motor 41. Motor 41 is a lowinertia d-c motor. Speed control of motor4l is one basic contributingfactor for obtaining the object of the present inventiomto ensure thatthe film passes the recording window 16 at aprecise rate withoutflutter, so that straight and equidistantly spaced lines are recorded.Furthermore, for each complete video frame the film has to advance overa distance precisely equal to the distance between two system sprocketholes. The motion of the sprocket capstan 40, therefore, requiresposition and speed control interacting at least to the extent thatposition and speed control do not counteract. Sprocket capstan 40 andmotor 41 are presumed to have a common shaft 42, or the equivalent forrotational synchronism. A tachometer disc. 50 is coupled for positiverotation with sprocket capstan 40.

Essentially element 50 is a transparent disc bearing contrast producingmarkers 51 along its periphery. The angular spacing of these markers isa precise duplication of the sprocket spacing on capstan 40, (it couldbe anintegral multiple). For reasons of simplification it follows thatthere are as many markers 51 on tachometer disc 50 as there aresprockets on capstan 40, and both are as accurately distantly spaced aspossible. The speed control for motor 41 is set up in such a manner thatcapstan 40 advances over an angle equal to sprocket and marker spacingduring one video frame period. v i

To obtain straight and equidistantly spaced lines it is necessary toobtain accurate speed control on a broadband basis, to eliminate higherfrequency vibrations, i.e., film 'flutter, and the like. The tachometer50 is,

therefore, provided with a second track of equidistantly spaced markers52 which are relatively large in number and represent the resolution ofspeed control. For practical purposes the number should be at leastcomparable with the number of lines per video frame; it can be the samenumber or even higher. There is, preferably, a fixed relation betweenthe number of markers 52 and markers 51,'i.e., the angle between any twosequential markers 51 is filled by the same number of markers 52. Themotor 41 is now controlled so that the markers 52 pass a stationarypoint at frequency and phase tracking frequency and phase of-a referencesignal, and the reference signal bears a fixed relation to the framerate.

The speed control for motor 41 is now provided as follows: The twomarker tracks on tachometer disc 50 are scanned by photoelectricdetectors, with markers 51 being scanned by detector 61 and markers 52being scanned by detector 62. Detectors 63 and-64, respectively, denoteoutput amplifiers for the two detectors 51 and the outputs,respectively, thereof operate toggle flip-flops 65 and 66. The outputsignals of toggle flipflops 65 and 66 are, therefore, square waves. Inparticular, flip-flop 65 furnishes a low-frequency square wave of halfthe sprocket frequency. The output square wave as provided by flip-flop66 is an integral multiple thereof, the factor being equal to number ofmarkers 52 per spacing of markers 51. As stated, the factor may be inthe order 10 or higher.

Sync separator 21 has an additional function, the separation of thevertical sync pulse from the composite video signal. This signal ispresumed to operate a toggle flip-flop 22, therefore, providing a squarewave output of half. the vertical frame frequency. The outputs of toggleflip-flops 22 and 65 are fed to different inputs of a phase detector 70,preferably a phase detector adjusted for processing particularly squarewave signals. Therefore, this phase detector 70 monitors thephaserelationship between the frame repetition rate of the video signal, onone hand, and of the relative sprocket positions as represented by theoutput of flip-flop 65, on the other hand. The control provided thecircuit to be described next is designed so that this phase detectorprovides a phase error zero. Implementation may require that phase,error zero be defined by a 180 out-of-phase of the square waves providedby flip-flops 22 and 65, which relation has to do merely with the choiceof the polarity of these signals.

A low bandpass filter 71 eliminates higher frequency components andripples from the output of phase detector so that a slowly varying do orlow frequency voltage is provided by filter 71 to a voltage controlledoscillator 72. VCO 72 is adjusted in that for an accurate phaserelationship, i.e., for a phase error zero, as defined, the frequency ofVCO 72 is precisely the frequency which detector-amplifier channel 6264will furnish for precisely the desired instantaneous speed of therotating system 41-40-50.

A toggle flip-flop 73 responds to the output of VCO 72 to reduce thefrequency by the factor of two to establish a reference frequency withwhich to compare the output frequency of toggle flip-flop 66. The twoflip-flops 66 and 73 now feed their outputs to a phase detector 74, aswell as to a frequency discriminator 75, the outputs of which are fed toa summing point 76.

The frequency discriminator 75 has preferably threshold behavior, inthat it provides a positive or a negative voltage of fixed amplitude tosumming point 76 for clamping the output of phase detector 74 to thatlevel. If flip-flops 73 and 66 provide signals of similar frequency butwith an undesired phase shift in between, clamping is removed, and thephase detector output takes over to provide a signal proportional inamplitude and sign to the instantaneous phase error.-

The output of summing point 76 is filtered by a filter 77 to removeswitching ripples. The filter output signal is fed to a loop amplifier78 which, in turn, feeds a driver amplifier 79, the output of whichcontrols d-c motor 41. it can readily be seen that higher frequencyvibrations in the film motion as noticeable near or at the capstan arecontrolled exclusively through the broadband feedback loop which derivesits input to be controlled from. the fine resolution marker track 52.The phase detector 70 will not, or hardly, respond tosuch vibrations butthe detector system 74-75 will respond as toggle flip-flop 66 varies inphase and even rate,due to speed variations in the rotary drive system.Since the film is positively gripped by the sprocket wheel, there is anintimate and direct relationship between film vibrations andoscillations of the sprocket capstan and by speed controlling thelatter, the film is pulled smoothly through the recording station.

The system is, of course, slaved to the frame rate as determined by theoutput pulses of sync separator 21, representing the vertical sync. Thesecond loop superimposes the desired position relationship betweensprocket holes, capstan sprockets and video frame rate. The referencesignal for the speed control is varied to establish and maintainphaseerror zero between vertical sync pulses and sprocket representation. Theposition control is essentially operating only at the beginning, to syncin the system. Thereafter, a phase error will be detected by detector 70only because of low frequency variations, either in the composite videosignal or in the capstan or both. In essence, these will be accumulatingresidual errors from several high frequency oscillations wherein thefine speed control has reestablished phase synchronism but with a phaseerror of 360 or an integral multiple thereof as to the wave train offlip-flop 66.

The resulting speed change in the film by operation of the narrow bandloop is a low frequency corrective which does not affect straightness ofthe video lines or spacing between adjacent pairs of lines. As thesystem is responsive to higher frequency control, the speed control loopthrough 52-64-66 tracks faithfully slow variations in the referencesignal path -71-72-73 for the speed control and is set up so that thebroadband loop establishes phase synchronism for the accurate positionbetween the frames as a whole and the sprocket hole sequence.

As stated, the tachometer 50 is constructed so that there is a fixed anddefinite relationship between the number of markers 52 per angulardistance between sprocket marker 51 and a normal" frequency is providedby VCO 72 for phase error zero in detector 70. It is thus apparent thatthe two controls for motor 41 provided in separate, but linked controlloops, do not disturb each other and do not act against each other. Thefine speed control, operating to maintain the speed of the film so thatthe phase between the two pulse trains from toggle flip-flop 73 and 66remains constant, inherently operates to maintain the sprocket positionin synchronism with the vertical sync pulses. This does not mean thatthe position control is superfluous, once synchronism between frames andsprockets is established, it merely means that the speed control, asprovided by the fine resolution broadband loop cannot stabilize at aphase error zero as between immediate sequences of pulses fromflip-flops 66 and 73, but the position control through detector 70,etc., ensures that there is no cumulative phase error and the squarewaves of 66 and 73 must return to synchronism always as if, on awave-for-wave basis there was never a deviation.

For starting the film drive, a normal tachometer 43 monitors the filmspeed and through a control circuit 44 dominates the input of amplifier79. As soon as the frequency discriminator 75 detects synchronism forthe first time, the circuit 44 is turned off and the double loop takesover.

lt-will be observed that the control accurately positions progressiveportions of the film in front of the recording slot or window 16, as thefilm is always positively engaged by the capstan sprocket 40. Thisincludes that progressive sprocket holes in the film approaching capstansprocket 40 are traversed respectively by a sprocket thereof in preciseposition for engagement. Nevertheless, the sprocket holes are never thataccurate so that there is sudden pushing and scraping as between anentering sprocket and edges of the respective sprocket hole. This tendsto set up vibrations within the film. To the extent these vibrationsaffect the sprocket capstan, they are not removed by the control loopsas described, but there are residual vibrations propagating toward thefilm portion facing window 16. Therefore, there is provided within thecircuit, a high inertia idler 45 positioned in close proximity torecording window 16, and a pulley 46 resiliently mounted on a compliancearm 47 ensures a partial loop engagement of the film around idler 45. Apositive and slippage-free engagement of the tensioned film against andwith heavy idler 45 establishes a nodal area for the film where engagingthe idler. Thus, nodes are set up in proximity of recording window 16 toprevent or at least impede oscillating motion of the film incrementinteracting with the recording beam. The heavy idler limits 9 also thedegree of oscillations film and capstan sprocket can undergo so that theamplitude of phase errors in the loop are ketp down particularly forhigher error frequencies. This in turn facilitates phase tracking by themotoricontrol loops.

FIGS. 2 and 3 illustrate the recording area in greater detail. Wallportion 151 pertains to the housing electron gun andhas theaperture 16.Underneath there is a second slot 161, and the slight pressuredifferential on both sides of the wall 151 gently draws the film 1 fiattowards recording window 16. The film edges rest against flat ledges 152and, 153 so that the emulsion, where to beexposed, is still freefloating and does not engage the wall portions above and below recordingslot 16. The heavy idler 45 is mounted in close proximity to the slot,sufficiently close so that the oscillation nodes in the film are asclose to the slot '16 as possible. The idler should, however, besomewhat displaced from the slot in direction longitudinalto the filmmotion as well as normal to the plane of the film. Otherwise, the idlerwould have to mechanically urge film 1 toward slot 16, which isdetrimental to the emulsion, even if there are ledges. Moreover,squeezing the'film through such gap establishes itself a source ofvibrations.

The compliance arm47 with idler 46 establishes a variable lengthbranchwithin film loop 33 between point 31, where the film leaves sprocketwheel to enter loop 33 and sprocket capstan 40 which branch includes therecording area. Compliance arm 47 takes up any changes in the amount offilm fed into film loop 33, i.e., arm 47 establishes a variablecapacitytemporary storage for a certain amount of film within loop 33. Ofcourse, the amount of film within the loop 33 is precisely constant atany instant as the length of film between portions 31 and 32 is fixed.That means that in case more film than normal enters the film loop, moreis withdrawn. However, capstan sprocket 40 as controlled enforces aprecisely constant passage rate of film in its vicinity and in vicinityof the recording area so-that the average speed of film within film loop33 must equal the capstan speed. Thus, sprocket wheels 40 and 30 must becoupled to the extent that at least,

on the average, the passage of film into and out of the loop isprecisely equal to the controlled speed of sprocket capstan 40. The twosprocket wheels 30 and 40, however, must be coupled so that theformercontrols the latter withoutfeedback, i.e., without having sprocketwheel'30 interfere with the controlled motion of capstan sprocket 40.

Elements 30 and 40 are coupled as follows: The amount of film in asecond branch of film loop 33 as between capstan 40 and point 32 ismonitored by a compliancearm acting as a feeler arm 80 with a pulley orthe like 81. For a particular lengthof film between sprocket capstan40and point 32, compliance arm 80 has a particular position; if there ismore or less film be tween capstan and point 32, arm 80 pivots in one orthe opposite direction. A vane 82 or the like on arm 80 is deflectedtherewith to act as variable shutter in the light path of a photocell83-lamp 84 arrangement monitoring the position of vane 82 and convertsthat varia tion in position into an electrical signal as developed inphotodetector 83. The output of detector 83 controls an amplifier 85which, in turn, controls a motor 86. Motor 86 drives sprocket wheel 30.The motor circuit may include a stabilizing loop, but the control inresponse to position of arm is also in a closed loop as speed changes inthe motor 86 will cause more or less film to be drawn from the film loopbranch between capstan 40 and point 32.

Generally the control operates so that motor 86 will increase the speedof sprocket wheel 30 in case capstan sprocket 40 feeds more film intoloop branch 40-32 than sprocket wheel 30 takes out, and the speedcontrol for motor 86 runs the opposite in case temporarily the filmlength between 40 and 32 declines. In essence, the sprocket wheel 30 iscoupled to sprocket 40 as the control for motor 86 forces sprocket wheeland capstan to run' in synchronism, whereby, however, the speedvariations of wheel 30 are hardly fed back as speed disturbances forcapstan 40. Any such disturbance should it occur, is, however,immediately corrected by the feedback control circuit for motor 41.

i It follows that there remains complete isolation of loop 33 fromirregularities in the tape reeling arrangement, which includes reels 10and 11, by operation of sprocket wheel 30.. The sprocket capstan 40control, therefore, has to respond only to temporary higher frequencyspeed disturbances within the loop 33 and does not have to balance lowfrequency and large amplitude disturbances in film transportation asthey may occur in the feed and takeup arrangement 10-l 1. Instead, thecontrol for motor 86 in a follower-type control loop slaved to sprocketcapstan 40 impedes or even inhibits these disturbances from propagatinginto the film loop 33. This loop has fixed film length by inherentoperation of sprocket wheel 30 and the control of motor 86 establishes aconstant loop branch 40-32. Loop branch 40-31 will thus be controlledindirectly to remain constant in length. I

In summary, the system operates for positioning film in front ofrecording window 16 in strict phase synchronism with the video signal ona frame-for-frame basis for continuous recording of straight,equidistantly spaced lines. Thisresult is obtained by combination of thenarrow-band position control of the film in response to sequentialpassage of film areas destined to receive recording respectively ofcomplete frames, by a broadband, high-frequency speed control, by a highinertia idler to eliminate higher frequency tape flutter, vibrations,etc., and by a film isolation loop indirectly coupled to the speedcontrolled sprocket capstan so that the average propagation rate of filmthrough the loop precisely equals the average sprocket capstan speed.

It should be mentioned that the control circuit could be modified inthat, for example, as illustrated in FIG.

4, the fine resolution track, as provided by the se-- quence ofregularly spaced markers 52 on tach disc 50 has a spatial rateequivalent to the horizontal line frequencies, i.e., there are as manymarkers 52 per marker 51 as there are lines in a frame. The referencesignals for the fine speed control will then be derived from syncseparator 21 operating as input and providing for separated input signalto be fed via a toggle flip-flop 24 as a reference to the phase andfrequency discriminator assembly 175, which includes the elements 74, 75and 76. The output of discriminator assembly is a dc signal processedfurther by filter and loop amplifier 178 and fed to driver amplifier 79via a switch 170. This establishes the nonnal operation for broadbandspeed control as described, slaving the film drive system linefor-lineto the video signal.

For position control, particularly prior to nonnal operation, the outputof phase detector 70 is used directly through an appropriate filter andamplifier circuit 177 for controlling'driver amplifier 79 directly, soas to establish, on a narrow-band basis, a particular constant phasebetween the tachometer disc representing the capstan sprockets and thevertical sync pulses. For this control, switch 170 has the alternativeposition whichis always established and maintained as long as phasedetector 70 detects a position phase error. When such phase synchronismhas been established, the output of phase detector 70 drops below theresponse threshold of switch control circuit 171 to change the positionof switch 170 to the illustrated position, and the system proceeds fromthere.

It is important to note that as long as there is only a phase error inthebroadband loop, there is inherently included a position control,because within the video signal has and maintains itself a fixedrelationship between vertical and horizontal sync pulses. Thus, once thevertical sync pulses have established an initial fixed phaserelationship between tach disc markers 51 and sprocket hole position,that phase can be maintained by considering horizontal sync pulses only.However, in case of broadband frequency error, the broadband loop maysync in the system to the wrong line sequence. This, however, isdetected by phase detector 70 and switch 170 changes position to bringthe control back into frame sprocket hole synchronism. Once thebroadband loop has taken over again, synchronism between horizontal syncpulses and high resolution tachometer pulses is established for thecorrect association as between marker sequence and video lines.

FIG. illustrates a second embodiment of the invention wherein a smoothcapstan 200 is used to advance the film in the loop in place of thesprocket capstan 40 shown in FIG. 1. All elements of the secondembodiment shown in FIG. 5 which are similar to elements shown in thefirst embodiments of FIG. 1 are given the same reference character. Forexample, the film l is pulled from the payout reel using the sprocketwheel 30. The film 1 passes over the idler wheel-46 supported at the endof the compliance arm 47.

The film -l is'then directed to and taken from the capstan 200 throughthe use of the idler wheels 202 and 204. After passing over the idlerwheel 204, the film then passes over the idler wheel 81 maintained atthe end of the compliance arm 80. The compliance arm 80 is used as thecontrol member in the servo system including the elements 82, 83 and 84so as to produce a signal in accordance with the position of thecomplaiance arm 80. The signal from the detector 83 is fed through theamplifier 85 to control the motor 86 which in turn drives the sprocketwheel 30. This servo system using the compliance arm 80 as the sensingelement is substantially the same as that shown in the first embodimentof FIG. 1.

The takeup reel 11 is drivenby the motor 12. The film l as it passesover the smooth capstan 200 is trans ported to pass by the window 16inthe electron gun 15.

In order to provide for the speed control of the motor 41 which drivesthe smooth capstan 200, the tachometer disc 50, which includes markers52, is used, and the markers are sensed by the detector 62. Thisstructure is substantially the same as the structure shown in the firstembodiment of FIG. 1. However, in the second embodiment of FIG. 5, thetachometer disc only includes markers 52 and the low frequency signal isproduced directly from the sprocket holes in the film 1 rather than theindirect system used in FIG. 1. This can be seen in FIG. 5 through theuse of a light source 206 which produces light energy which is directedthrough the sprocket holes in the film 1 by the lens 208 which lightenergy impinges on photodetector 210. The output from the photodetector210 is supplied to the amplifier 63 which is the same as the amplifier63 of FIG. 1. The remaining elements of the speed control system aresubstantially identical to those shown in FIG. 1 and reference is madeto the description of these elements under the description of theembodiment of FIG. 1.

The second embodiment of the invention shown in FIG. 5 thereforeincludes a smooth capstan to advance the film in the loop in place ofthe sprocket capstan. The use of the smooth capstan in place of thesprocket capstan eliminates the high frequency vibration caused by thesprockets entering and leaving the sprocket holes. This isreferred to assprocket tooth ripple, and such sprocket tooth ripple was eliminated inthe first embodiment of the invention using the high-inertia idler. Thesecond embodiment of the invention is therefore simpler in construction.

Another difference in the second embodiment of the invention ascontrasted with the first embodiment of the invention is the detectionof the low-frequency signal for the speed control directly from the filmby monitoring the sprocket holes. This is contrasted with the use of asecond track on the tachometer disc to provide an indirect detection ofthe sprocket holes of the embodiment of FIG. 1.

A third embodiment of the invention as shown in FIG. 6 includes furthermodifications relating to the film drive. Elements in the thirdembodiment of the invention which are similar to either of those shownin FIGS. 1 and 5 are given the same reference characters. In the thirdembodiment of the invention shown in FIG. 6, the film 1 is directlydriven from the payout reel 10 to the takeup reel 11 and the sprocketwheel drive is eliminated. Specifically, in FIG. 6 the film as drivenfrom the payout reel 10 passes over an idler roller 250. The film thencontinues around an idler roller 252 maintained at the end of acompliance arm 25.4. The film path then continues around idler roller202, smooth capstan 200, idler roller 204 and around an idler roller256, which is maintained at the end of a compliance arm 258. An idlerroller 260 completes the path back to the takeup reel 11.

The compliance arms 254 and 258 are used to provide servoing of themotor drive for the payout reel 10 and takeup reel 11. Specifically, avane element or the like 262 is coupled to the compliance arm 254 andacts as a variable shutter in the light path of a photocell 264 andlight source 266. The position of the variable shutter 262 is monitoredand converted into an electrical signal which is developed in thephotodetector 264. The output of the detector 264 controls an amplifier268 which in turn controls a motor 270 which drives the payout reel 10.

A similar arrangement including a variable vane 272, light source 274, aphotodetector 276, and an amplifier 278 is used to provide a signal tocontrol the motor 12 which drives the takeup reel 11. p

This double compliance ann servoing of the payout and takeup reelsprovides for a substantially constant flow of film l and specifically asubstantially constant 13 tension and film length in the film loopbetween the payout and takeup reels.

The smooth capstan 200 provides for a particular control of the filmsothat the recording of information is properly spaced relative to thesprocket holes and the motor. drive and speed control for the smoothcapstan 200 is essentially described with reference to the embodimentsof the invention shown in FIGS. 1 through 6 scribed above, but allchanges and modifications I thereof not constituting departures from thespirit and scope of the invention are intended to be included.

1. In a system for transporting through a recording area photographicfilm running from'a payout reel to a takeup reel, the combinationcomprising:

first means including a sprocket wheel engaging the film for providingafilm loop of fixed length between two points to obtain a feeding offilm into the loop at one of the two points and out of the loop at thesame rate at the other one of the two points;

second means including a capstan engaging the film inside of the loopfor imparting motion upon the film, the second means further includingmeans providing a closed loop servo responsive to the speed of thecapstan to control the movement of the capstan to obtain a particularrate of progression of the filmithrough the recording area within theloop; and, r I

means including a second servo responsive to the instantaneous length offilm between the capstan and a particular one of the two points andoperatively coupled to the sprocket wheel for driving the sprocket wheelat a speed variable in accordance with variations in such instantaneouslengths of the film to control the speed of the film between the capstanand the particular point to maintain the length of the film between thecapstan and the particular point substantially constant.

2. In a system for transporting through-a recording area photographicfilm running from apayout reel to atakeup reel, the combinationcomprising:

first means including a sprocket wheel engaging the film for providing afilm loop of fixed length between two points to obtain a feeding of filminto the loop at one of the two points and out of the loop at the samerate at the other one of the two points;

second means including a capstan engaging the film inside of the loopfor imparting motion upon the film, the second means further includingmeans providing a closed loopservo to control the movement of thecapstan to obtain aparticular rate of progression of the film throughthe recording area within the loop; a d

- means responsive to the instantaneous length of film between thecapstan and a particular one of the two points and operatively coupledto the sprocket wheel for controlling the speed of the film between dthe capstan and the particular point to maintain the length of the filmbetween the capstan and the particular point substantially constant,

an idler of relatively high inertia for engaging the film in thevicinity of the recording area; and

means tensioning the film against the idler to run in slippage-freefrictional engagement with the film.

3. In a system as set forth in claim 2, the high inertia idler beingpositioned on the film in the branch of the loop extending between thecapstan and the other one of the two points.

4. In a system for transporting through a recording area photographicfilm running from a payout reel to a takeup reel there being sprocketholes in the film and information being recorded in frames on the filmand the frames being formed from successivelines of information, thecombination comprising:

first means including a sprocket wheel engaging the film for providing afilm loop of fixed length between two points to obtain a feeding of filminto the loop at one of the two points and out of the loop at the samerate at the other one of the two points;

second means including a capstan engaging the film inside of the loopfor imparting motion upon the film, the second means further includingmeans providing a closed loop servo to control the movement of thecapstan to obtain a particular rate of progression of the film throughthe recording area within the loop; Y means including a second servoresponsive to the instantaneous length of film between the capstan and'aparticular one of the two points and operatively coupled to thesprocket wheel for driving the sprocket wheel at a speed variable inaccordance with variations in such instantaneous lengths of the film tocontrol the speed of the film between the capstan and the particularpoint to maintain the length of the film between the capstan and theparticular point substantially constant; third means providing lowfrequency representation of progression and relative position of thesprocket holes within the loop to indicate the successive frames ofinformation;

fourth means providing relatively high frequency representation ofprogression of the film within the loop to indicate the successive linesof information within each frame;

fifth means providing video signals including sync signals; and

sixth means included in the closed loop servo means in the second meansand responsive to the sync signals and the representations provided bythe third means and the fourth means for controlling the movement of thecapstan.

5. In a system as set forth in claim 4, sixth means included within theclosed loop servo means in the second means and responsive to theprogression of the frames to be recorded on the film for comparing therepresentation thereof relative to the representation as provided by thethird means to control the movements of the capstan in accordance withsuch comparison.

6. In a system as set forth in claim 5, the sixth means providing areference signal varying in frequency with variations in the phase, thefifth means comparing the reference signal with the representation asprovided by the fourth means to control the speed of the capstan so asto obtain a particular relation between the compared signals.

7. In a system as set forth in claim 4, the second means including a lowinertia member for driving the capstan, the system further including arelatively high inertia idler coupled to the film between the capstanand the other one of the points in the vicinity of the recording area.

8. In a system for recording video signals in sequential frames, eachframe to be composed of a similar plurality of equidistantly spacedlines, on a photographic film by means of a beam of radiant energy,there being .a supply reel and a takeup reel for the film, thecombination comprising: i

a sprocket capstan for engaging the sprocket holes in the film to movethe film past an area for interaction with the beam;

first means coupled to the capstan for driving the capstanand includingmeans for providing first signals in representation of progression ofcapstan and film, and'second signals having particular relation to thefirst signals and provided in representation of progressing sprocketpositions of thesprocket capstan;

second means including a source of reference signals and responsive tothe first signals and the reference signals to control the first meansto obtain particular phase between first and reference signals; and

third means connected to be responsive to the progression of frames asrepresented in the video signals and further responsive to the secondsignals to obtain third signals in representation of the relativepositions of frames and sprocket holes in the film and connected to thesecond means to control the first means in response to the third signalsto maintain a particular relation between recorded frames and sprocketsholes.

9. In a system as set forth in claim 8, including a sprocket wheelcoupled to the film to isolate a fixed portion of the .film from supplyand takeupreels, the sprocket capstan engaging the film in the isolatedportion, and means to control the sprocket wheel in response toprogression of the sprocket capstan.

10. In a system as set forth in claim 8, including an idler ofrelatively heavy mass frictionally and slippagefree coupled to the filmin the vicinity of the recording area.

11. In a system as set forth in claim 8, the third means controlling thefirst means and overriding the control as provided by the second means.

12. In a system as set forth in claim 8, the third means being connectedto the second means in that the reference signals are derived from thethird signals.

13. In a system as set forth in claim 8, there being means 'to separatevertical synchronization pulses from the video signals, the first meansincluding means rotating with the sprocket capstan to provide the secondsignals, the third means providing phase representation as between thevertical synch pulses and the second signals, the third signalscontrolling a voltage controlled oscillation serving as source ofreference signals in the second means.

14. In a-system as set forth in claim 8, there being means to separatehorizontal and vertical synchronization pulses from the video signals,the horizontal synch pulses serving as reference signals in the secondmeans,

the vertical synch pulses being compared with the second signals in thethird means to provide the third signals, and means to place the firstmeans under control of the third or the second means, respectively, inresponse to absence or presence of the particular relation.

15. In a system for transporting photographic film past a region forrecording thereon, the combination comprising:

a sprocket wheel for engaging the film in opposite points andestablishing a constant length loop; asprocket capstan for engaging thefilm in the loop to move the film through the region;

means coupled to the sprocket wheel to control the motion of thesprocket wheel to maintain a particular film length between the capstanand the sprocket wheel;

a low inertia motor for driving the capstan;

a high inertia idler engaging the film in the loop and in the vicinityof the region; and

means coupled to the film for tensioning the film in a partial loopagainst the high inertia idler. 16. In a system for transporting filmhaving sprocket holes running from a payout reel to a takeup reel, thecombination comprising:

first means for providing a film loop of fixed length between twopoints, feeding film into the loop at one of the two points and out ofthe loop at approximately the same rate at the other one of the twopoints; second means including a capstan engaging the film inside of theloop for imparting motion upon the film, further including means tocontrol the capstan .in accordance with the rate of progression of thesprocket holes to obtain a particular rate of progression of the filmthrough a particular area within the loop; and

third means responsive to the instantaneous length of film between thecapstan and at least one of the points and coupled to the first meansfor maintaining the latter length substantially constant.

17. In a system as set forth in claim 16 wherein the first meansincludes a sprocket wheel engaging the sprocket holes of the film at thetwo points.

18. In a system as set forth in claim 16 wherein the first meansincludes drive means for the payout and takeup reels and the two pointsare the payout and takeup reels.

19. In a system as set forth in claim 16 wherein the second meansincludes fourth means providing representation of progression andrelative position of the sprocket holes within the loop; and

fifth means also included in the second means for controlling thecapstan in response to the representations provided by the fourth means.

20. In a system as set forth in claim 19 wherein the fourthmeansadditionally provides relative high frequency representation of theprogression of the film within the loop.

21. In a system for providing movement of a film having sprocket holes,there being a supply reel and a takeup reel for the film, thecombination comprising:

a capstan for engaging the film to move the film past an area forinteraction;

17 in representation of progression of the capstan and including meansfor providing second signals in representation of progressing sprocketholes of the film; r i

second means including a source of reference signals and responsive tothe second signals to compare the reference signals and the secondsignals to produce a third signal; and third means for comparing thefirst signals and the third signals to produce a fourthsignal inaccordance with such comparison and with the fourth signal providing acontrol of the first means for obtaining a particular phase between thesecond and reference signals and for producing a particular movement ofthe capstan. 22. In a system for transporting from a payout reel to atakeup reel film having sprocket holes and for recording videoinformation on the film in successive frames and successive lines ofinformation within each frame in accordance'with video signals havingsync signals, the combination comprising:

first means for providing a film loop of fixed length;

viding a control signal representative of the pro-* gression andrelative position of the sprocket holes;

fourth means including a first servocoupled 'to the second and thirdmeans and responsive to the control signal and the video sync signalsfor controlling the movements of the capstan in accordance withsuchcomparison to obtain a particular rate of progression of the filmwithin the loop; and fifth means including a second servo responsive tothe relative length of film at each instant between the particularposition and the sprocket for driving the sprocket at aspeed adjustablein accordance with such relative length of film at each instant tomaintain such length of film substantially constant at each instant. r v23. In a system as set forth in claim22 wherein the third. meansprovides for a direct monitoring of the sprocket holes in the film andthe capstan is a sprocket capstan.

24. In a system as set forth in claim 22 wherein the third meansprovides for an indirect monitoring of the sprocket holes.

25. In a system for transporting film from a payout reel to a takeupreel,

first means for engaging the film at a pair of spaced positions on thefilm to provide a loop of fixed length between the pair of spacedpositions and for driving the film at the pair of spaced positions,

capstan means engaging the film at a particular position between thepair of spaced positions to drive the film,

. first sensing means for sensingthe movement of the film between afirst one of the spaced positions and the capstan means to providefirstcontrol signals,

second'sensing means for sensing the movement of the film between hecapstan means and the other one of the spaced positions to providesecond control signals,

first servo means responsive to the first control signals forcontrolling the operation of the capstan means in driving the filmbetween the pair of spaced positions, and

second servo means responsive to the second control signals forcontrolling the operation of the first means in driving the film at thepair of spaced positions. I

26. In the system set forth in claim 25, wherein means are included forproviding video information to be recorded in successive frames andsuccessive lines of information within each frame and for providingvertical sync signals defining the successive frames and wherein thefirst servo means are re sponsive to the vertical sync signals and thefirst control signals for comparing such signals to control theoperation of the capstan means in accordance with such comparison andwherein means are disposed near the capstan for recording the videoinformation on the film. 1

27. In the system set forth in claim 26,

a high inertia idler engaging the film at a position be- ,tween thefirst one of the spaced positions and the capstan means to impedeoscillations of the film between the first one'of the spaced positionsand the capstan means.-

28. In the system set forth in claim 26,

the film-having sprocket holes,

the first sensing means including means for producing the first controlsignals in accordance with the movements of the sprocket holes on thefilm past the capstan means and for producing third control signals inaccordance with incremental movements of the film past the capstan meansin the intervals between the successive sprocket holes,

the first servo means including means for producing signals of avariable frequency in accordance with the comparison between thevertical sync signals and the first control signals,

the first servo means also including means responsive to the thirdcontrol signals and the signals of variable frequency for comparing suchsignals to control the operation of thecapstan means in accordance with.such comparison.

29. In the system Setforth in claim 28,

the recording means being disposed at a position between the first oneof the spaced positions and the capstan means and a high inertia idlerbeing disposed between the first one of the spaced positions and therecordingjmeans to impede oscillations of the film during the movementof the film past the recording means.

30. In a system for transporting through a recording areav P otographicfilm running from a payout reel to a takeup reel, the combinationcomprising:

first means including a sprocket wheel engaging the film for providing afilm loop of fixed length between two points to obtain a feeding of thefilm into the loop at one of the two points and out of the loop at thesame rate at the other one of the two points, 7

second means including a capstan engaging the film inside of the loopfor imparting motion to the film,

third means disposed between the capstan and one of the two points forsensing the tension of the film between the capstan and the one of thetwo points to produce a signal representing such tension,

fourth means operatively coupled to the sprocket wheel for driving thesprocket wheel, and

fifth means responsive to the signal representing the tension of thefilm and operatively coupled to the fourth means for controlling theoperation of the fourth means in driving the sprocket wheel inaccordance with the characteristics of the signal.

31. In a system as set forth in claim 30,

means disposed between the capstan and the other one of the two pointsfor recording video information on the film. 32. In a system as setforth in claim 30, means operatively coupled to the capstan forcontrolling the operation of the capstan to control the positions atwhich the video information is recorded on the film. 33. In a system fortransporting from a payout reel to a takeup reel film having sprocketholes and for recording video information on the film in successiveframes and successive lines of information within each frame inaccordance with video signals having sync signals, the video signalshaving vertical sync signals for each frame, the combination comprising:

first means for providing a film loop of fixed length;

second means including a capstan engaging the film within the loop forimparting motion to the film; third means responsive to the sprocketholes for providing a control signal representative of the progressionand relative position of the sprocket holes;

and fourth means coupled to the second and third means and responsive tothe control signal and the video sync signals for controlling themovements of the capstan in accordance with such comparison to obtain aparticular rate of progression of the film first means for providing afilm loop of fixed length;

second means including a capstan engaging the film within the loop forimparting motion to the film;

third means responsive to the sprocket holes for providing a controlsignal representative of the progression and relative position of thesprocket holes; and

fourth means coupled to the second and third means and responsive to thecontrol signal and the video sync signals for controlling the movementsof the capstan in accordance with such comparison to obtain a particularrate of progression of the film within the loop, the fourth meansincluding first servo means for comparing the control signal and thevideo sync signals to provide signals having a variable frequency inaccordance with such comparison and the third means including means forproviding second control signals representing incremental movements ofthe capstan between successive sprocket holes in the film and the fourthmeans including second servo means responsive to the second controlsignals and the signals of variable frequency from the first servo meansto control the movement of the capstan.

1. In a system for transporting through a recording area photographicfilm running from a payout reel to a takeup reel, the combinationcomprising: first means including a sprocket wheel engaging the film forproviding a film loop of fixed length between two points to obtain afeeding of film into the loop at one of the two points and out of theloop at the same rate at the other one of the two points; second meansincluding a capstan engaging the film inside of the loop for impartingmotion upon the film, the second means further including means providinga closed loop servo responsive to the speed of the capstan to controlthe movement of the capstan to obtain a particular rate of progressionof the film through the recording area within the loop; and meansincluding a second servo responsive to the instantaneous length of filmbetween the capstan and a particular one of the two points andoperatively coupled to the sprocket wheel for driving the sprocket wheelat a speed variable in accordance with variations in such instantaneouslengths of the film to control the speed of the film between the capstanand the particular point to maintain the length of the film between thecapstan and the particular point substantially constant.
 2. In a systemfor transporting through a recording area photographic film running froma payout reel to a takeup reel, the combination comprising: first meansincluding a sprocket wheel engaging the film for providing a film loopof fixed length between two points to obtain a feeding of film into theloop at one of the two points and out of the loop at the same rate atthe other one of the two points; second means including a capstanengaging the film inside of the loop for imparting motion upon the film,the second means further including means providing a closed loop servoto control the movement of the capstan to obtain a particular rate ofprogression of the film through the recording area within the loop;means responsive to the instantaneous length of film between the capstanand a particular one of the two points and operatively coupled to thesprocket wheel for controlling the speed of the film between the capstanand the particular point to maintain the length of the film between thecapstan and the particular point substantially constant, an idler ofrelatively high inertia for engaging the film in the vicinity of therecording area; and means tensioning the film against the idler to runin slippage-free frictional engagement with the film.
 3. In a system asset forth in claim 2, the high inertia idler being positioned on thefilm in the branch of the loop extending between the capstan and theother one of the two points.
 4. In a system for transporting through arecording area photographic film running from a payout reel to a takeupreel there being sprocket holes in the film and information beingrecorded in frames on the film and the frames being formed fromsuccessive lines of information, the combination comprising: first meansincluding a sprocket wheel engaging the film for providing a film loopof fixed length between two points to obtain a feeding of film into theloop at one of the two points and out of the loop at the same rate atthe other one of the two points; second means including a capstanengaging the film inside of the loop for imparting motion upon the film,the second means further including means providing a closed loop servoto control the movement of the capstan to obtain a particular rate ofprogression of the film through the recording area within the loop;means including a second servo responsive to the instantaneous length offilm between the capstan and a particular one of the two points andoperatively coupled to the sprocket wheel for driving the sprocket wheelat a speed variable in accordance with variations in such instantaneouslengths of the film to control the speed of the film between the capstanand the particular point to maintain the length of the film between thecapstan and the particular point substantially constant; third meansproviding low frequency representation of progression and relativeposition of the sprocket holes within the loop to indicate thesuccessive frames of information; fourth means providing relatively highfrequency representation of progression of the film within the loop toindicate the successive lines of information within each frame; fifthmeans providing video signals including sync signals; and sixth meansincluded in the closed loop servo means in the second means andresponsive to the sync signals and the representations provided by thethird means and the fourth means for controlling the movement of thecapstan.
 5. In a system as set forth in claim 4, sixth means includedwithin the closed loop servo means in the second means and responsive tothe progression of the frames to be recorded on the film for comparingthe representation thereof relative to the representation as provided bythe third means to control the movements of the capstan in accordancewith such comparison.
 6. In a system as set forth in claim 5, the sixthmeans providing a reference signal varying in frequency with variationsin the phase, the fifth means comparing the reference signal with therepresentation as provided by the fourth means to control the speed ofthe capstan so as to obtain a particular relation between the comparedsignals.
 7. In a system as set forth in claim 4, the second meansincluding a low inertia member for driving the capstan, the systemfurther including a relatively high inertia idler coupled to the filmbetween the capstan and the other one of the points in the vicinity ofthe recording area.
 8. In a system for recording video signals insequential frames, each frame to be composed of a similar plurality ofequidistantly spaced lines, on a photographic film by means of a beam ofradiant energy, there being a supply reel and a takeup reel for thefilm, the combination comprising: a sprocket capstan for engaging thesprocket holes in the film to move the film past an area for interactionwith the beam; first means coupled to the capstan for driving thecapstan and including means for providing first signals inrepresentation of progression of capstan and film, and second signalshaving particular relation to the first signals and provided inrepresentation of progressing sprocket positions of the sprocketcapstan; second means including a source of reference signals andresponsive to the first signals and the reference signals to control thefirst means to obtain particular phase between first and referencesignals; and third means connected to be responsive to the progressionof frames as represented in the video signals and further responsive tothe second signals to obtain third signals in representation of therelative positions of frames and sprocket holes in the film andconnected to the second means to control the first means in response tothe third signals to maintain a particular relation between recordedframes and sprockets holes.
 9. In a system as set forth in claim 8,including a sprockeT wheel coupled to the film to isolate a fixedportion of the film from supply and takeup reels, the sprocket capstanengaging the film in the isolated portion, and means to control thesprocket wheel in response to progression of the sprocket capstan. 10.In a system as set forth in claim 8, including an idler of relativelyheavy mass frictionally and slippage-free coupled to the film in thevicinity of the recording area.
 11. In a system as set forth in claim 8,the third means controlling the first means and overriding the controlas provided by the second means.
 12. In a system as set forth in claim8, the third means being connected to the second means in that thereference signals are derived from the third signals.
 13. In a system asset forth in claim 8, there being means to separate verticalsynchronization pulses from the video signals, the first means includingmeans rotating with the sprocket capstan to provide the second signals,the third means providing phase representation as between the verticalsynch pulses and the second signals, the third signals controlling avoltage controlled oscillation serving as source of reference signals inthe second means.
 14. In a system as set forth in claim 8, there beingmeans to separate horizontal and vertical synchronization pulses fromthe video signals, the horizontal synch pulses serving as referencesignals in the second means, the vertical synch pulses being comparedwith the second signals in the third means to provide the third signals,and means to place the first means under control of the third or thesecond means, respectively, in response to absence or presence of theparticular relation.
 15. In a system for transporting photographic filmpast a region for recording thereon, the combination comprising: asprocket wheel for engaging the film in opposite points and establishinga constant length loop; a sprocket capstan for engaging the film in theloop to move the film through the region; means coupled to the sprocketwheel to control the motion of the sprocket wheel to maintain aparticular film length between the capstan and the sprocket wheel; a lowinertia motor for driving the capstan; a high inertia idler engaging thefilm in the loop and in the vicinity of the region; and means coupled tothe film for tensioning the film in a partial loop against the highinertia idler.
 16. In a system for transporting film having sprocketholes running from a payout reel to a takeup reel, the combinationcomprising: first means for providing a film loop of fixed lengthbetween two points, feeding film into the loop at one of the two pointsand out of the loop at approximately the same rate at the other one ofthe two points; second means including a capstan engaging the filminside of the loop for imparting motion upon the film, further includingmeans to control the capstan in accordance with the rate of progressionof the sprocket holes to obtain a particular rate of progression of thefilm through a particular area within the loop; and third meansresponsive to the instantaneous length of film between the capstan andat least one of the points and coupled to the first means formaintaining the latter length substantially constant.
 17. In a system asset forth in claim 16 wherein the first means includes a sprocket wheelengaging the sprocket holes of the film at the two points.
 18. In asystem as set forth in claim 16 wherein the first means includes drivemeans for the payout and takeup reels and the two points are the payoutand takeup reels.
 19. In a system as set forth in claim 16 wherein thesecond means includes fourth means providing representation ofprogression and relative position of the sprocket holes within the loop;and fifth means also included in the second means for controlling thecapstan in response to the representations provided by the fourth means.20. In a system as set forth in claim 19 wherein the fourtH meansadditionally provides relative high frequency representation of theprogression of the film within the loop.
 21. In a system for providingmovement of a film having sprocket holes, there being a supply reel anda takeup reel for the film, the combination comprising: a capstan forengaging the film to move the film past an area for interaction; firstmeans for controlling the movement of the capstan and including meansfor providing first signals in representation of progression of thecapstan and including means for providing second signals inrepresentation of progressing sprocket holes of the film; second meansincluding a source of reference signals and responsive to the secondsignals to compare the reference signals and the second signals toproduce a third signal; and third means for comparing the first signalsand the third signals to produce a fourth signal in accordance with suchcomparison and with the fourth signal providing a control of the firstmeans for obtaining a particular phase between the second and referencesignals and for producing a particular movement of the capstan.
 22. In asystem for transporting from a payout reel to a takeup reel film havingsprocket holes and for recording video information on the film insuccessive frames and successive lines of information within each framein accordance with video signals having sync signals, the combinationcomprising: first means for providing a film loop of fixed length;second means including a capstan engaging the film at a particularposition within the loop for imparting motion to the film; third meansresponsive to the sprocket holes for providing a control signalrepresentative of the progression and relative position of the sprocketholes; fourth means including a first servo coupled to the second andthird means and responsive to the control signal and the video syncsignals for controlling the movements of the capstan in accordance withsuch comparison to obtain a particular rate of progression of the filmwithin the loop; and fifth means including a second servo responsive tothe relative length of film at each instant between the particularposition and the sprocket for driving the sprocket at a speed adjustablein accordance with such relative length of film at each instant tomaintain such length of film substantially constant at each instant. 23.In a system as set forth in claim 22 wherein the third means providesfor a direct monitoring of the sprocket holes in the film and thecapstan is a sprocket capstan.
 24. In a system as set forth in claim 22wherein the third means provides for an indirect monitoring of thesprocket holes.
 25. In a system for transporting film from a payout reelto a takeup reel, first means for engaging the film at a pair of spacedpositions on the film to provide a loop of fixed length between the pairof spaced positions and for driving the film at the pair of spacedpositions, capstan means engaging the film at a particular positionbetween the pair of spaced positions to drive the film, first sensingmeans for sensing the movement of the film between a first one of thespaced positions and the capstan means to provide first control signals,second sensing means for sensing the movement of the film between hecapstan means and the other one of the spaced positions to providesecond control signals, first servo means responsive to the firstcontrol signals for controlling the operation of the capstan means indriving the film between the pair of spaced positions, and second servomeans responsive to the second control signals for controlling theoperation of the first means in driving the film at the pair of spacedpositions.
 26. In the system set forth in claim 25, wherein means areincluded for providing video information to be recorded in successiveframes and successive lines of information within each frame and forproviding vertical sync sIgnals defining the successive frames andwherein the first servo means are responsive to the vertical syncsignals and the first control signals for comparing such signals tocontrol the operation of the capstan means in accordance with suchcomparison and wherein means are disposed near the capstan for recordingthe video information on the film.
 27. In the system set forth in claim26, a high inertia idler engaging the film at a position between thefirst one of the spaced positions and the capstan means to impedeoscillations of the film between the first one of the spaced positionsand the capstan means.
 28. In the system set forth in claim 26, the filmhaving sprocket holes, the first sensing means including means forproducing the first control signals in accordance with the movements ofthe sprocket holes on the film past the capstan means and for producingthird control signals in accordance with incremental movements of thefilm past the capstan means in the intervals between the successivesprocket holes, the first servo means including means for producingsignals of a variable frequency in accordance with the comparisonbetween the vertical sync signals and the first control signals, thefirst servo means also including means responsive to the third controlsignals and the signals of variable frequency for comparing such signalsto control the operation of the capstan means in accordance with suchcomparison.
 29. In the system set forth in claim 28, the recording meansbeing disposed at a position between the first one of the spacedpositions and the capstan means and a high inertia idler being disposedbetween the first one of the spaced positions and the recording means toimpede oscillations of the film during the movement of the film past therecording means.
 30. In a system for transporting through a recordingarea photographic film running from a payout reel to a takeup reel, thecombination comprising: first means including a sprocket wheel engagingthe film for providing a film loop of fixed length between two points toobtain a feeding of the film into the loop at one of the two points andout of the loop at the same rate at the other one of the two points,second means including a capstan engaging the film inside of the loopfor imparting motion to the film, third means disposed between thecapstan and one of the two points for sensing the tension of the filmbetween the capstan and the one of the two points to produce a signalrepresenting such tension, fourth means operatively coupled to thesprocket wheel for driving the sprocket wheel, and fifth meansresponsive to the signal representing the tension of the film andoperatively coupled to the fourth means for controlling the operation ofthe fourth means in driving the sprocket wheel in accordance with thecharacteristics of the signal.
 31. In a system as set forth in claim 30,means disposed between the capstan and the other one of the two pointsfor recording video information on the film.
 32. In a system as setforth in claim 30, means operatively coupled to the capstan forcontrolling the operation of the capstan to control the positions atwhich the video information is recorded on the film.
 33. In a system fortransporting from a payout reel to a takeup reel film having sprocketholes and for recording video information on the film in successiveframes and successive lines of information within each frame inaccordance with video signals having sync signals, the video signalshaving vertical sync signals for each frame, the combination comprising:first means for providing a film loop of fixed length; second meansincluding a capstan engaging the film within the loop for impartingmotion to the film; third means responsive to the sprocket holes forproviding a control signal representative of the progression andrelative position of the sprocket holes; and fourth means coupled to thesecond and third means and responsive to the control signal and thevideo sync signals for controlling the movements of the capstan inaccordance with such comparison to obtain a particular rate ofprogression of the film within the loop, the fourth means includingclosed loop servo means for comparing the control signal and the videosync signals to control the movement of the capstan in accordance withsuch comparison.
 34. In a system for transporting from a payout reel toa takeup reel film having sprocket holes and for recording videoinformation on the film in successive frames and successive lines ofinformation within each frame in accordance video signals having syncsignals, the video signals having vertical sync signals for each frame,the combination comprising: first means for providing a film loop offixed length; second means including a capstan engaging the film withinthe loop for imparting motion to the film; third means responsive to thesprocket holes for providing a control signal representative of theprogression and relative position of the sprocket holes; and fourthmeans coupled to the second and third means and responsive to thecontrol signal and the video sync signals for controlling the movementsof the capstan in accordance with such comparison to obtain a particularrate of progression of the film within the loop, the fourth meansincluding first servo means for comparing the control signal and thevideo sync signals to provide signals having a variable frequency inaccordance with such comparison and the third means including means forproviding second control signals representing incremental movements ofthe capstan between successive sprocket holes in the film and the fourthmeans including second servo means responsive to the second controlsignals and the signals of variable frequency from the first servo meansto control the movement of the capstan.